The Justice Department has sued the city of Houston over sex discrimination claims launched by two female firefighters who say their male coworkers tormented them by urinating on the women's bathroom walls and sinks and scrawling vulgar slurs on their belongings.

Male firefighters allegedly turned off the cold water in showers to scald their female coworkers and disconnected speakers to prevent women from responding to calls in a string of bad behavior that eventually escalated to death threats, according to the lawsuit.

"Far too often, women are targeted and harassed in the workplace because of their sex," said Acting Assistant Attorney General John Gore of the Civil Rights Division. "Employees have the right to work in an environment that is free from sex discrimination and retaliation."

The conduct continued over time despite at least nine complaints to management, which failed to remedy the situation and allegedly created a hostile work environment for firefighters Jane Draycott and Paula Keyes.

The city did not comment on the suit, while the firefighters' union pushed to see more evidence released in the case and decried long-standing criticism of the department.

"Dozens of firefighters cooperated in the various investigations of this incident, but unfounded criticism of Houston firefighters has continued for years," Houston Professional Fire Fighters Association President Marty Lancton said.

The claims at the center of the DOJ case first drew attention nearly ten years ago, when Draycott and Keyes reported finding racist and sexist graffiti scrawled on the women's dorm walls in summer 2009.

But the problems started months before that, according to court filings. As the only women working at Station 54 when they started, Draycott and Keyes were often ignored for entire shifts when their male coworkers refused to talk to them or eat with them.

"In early 2009, Draycott reported to her Captain that a firecracker exploded when she opened the door to the stall in the women's bathroom," the suit says. "He laughed at her complaint."

Repeatedly, they found urine on the sink and toilet in the women's bathroom, trash on their beds and cables missing from their TVs, according to court papers.

Then on July 7 - eight days after Draycott filed a sex discrimination complaint - the women showed up for work and found the n-word and "die b****" written on the walls.

Inside Draycott's locker, someone wrote "dead" on a picture of her daughter who'd been killed in a car wreck and "die" on a picture of Draycott, according to filings.

At the time, department was already reeling amid other racial discrimination accusations after two noose-like knots were found in firehouses.

The FBI and the city's Office of Inspector General both looked into the women's allegations, but in the end they decided there wasn't enough evidence to pinpoint a culprit.

The scandal, nevertheless, cast a shadow over HFD, and was one factor that led then-Mayor Annise Parker to search for an outside candidate to lead the department.

When Draycott returned to work in early 2010 following her complaints, she alleged, HFD retaliated against her by letting her coworkers publicly disparage her.

At one point, she filed suit against the department, detailing the summer 2009 graffiti incident and alleging sex discrimination dating back to 2000. But in mid-2010 she dropped the claim.

Draycott was ultimately forced into early retirement due to "intolerable" working conditions, according to the Justice Department.

The DOJ lawsuit follows an Equal Employment Opportunity Commission finding in favor of the two women at the center of the claim. Other women who previously had worked at the same station made similar complaints - but the department failed to act, the lawsuit alleges.

The legal action seeks to force HFD to develop policies to prevent sex discrimination and retaliation, but it also asks for monetary relief for Draycott and Keyes, according to a press release.

"No employee should be subjected to a hostile work environment based on their sex," U.S. Attorney Ryan K. Patrick said. "We will aggressively protect employees who are victims of sex discrimination and retaliation and pursue employers who violate the law."

The mayor's office initially declined Wednesday to comment on the new lawsuit.

"The Mayor's Office of Communications learned about the lawsuit through media reports this afternoon," spokeswoman Mary Benton said in an email. "At this time, we do not have a comment."

Representatives from the firefighters' union said the lawsuit underscored the need for city officials to make public the findings of an investigation involving 40 firefighters that were polygraphed and who gave sworn statements or handwriting samples during the investigation.

"From the beginning of this controversy, Houston firefighters have wanted the perpetrator(s) of the incidents at Station 54 found and punished appropriately," Lancton said, in an emailed statement.

The union leader emphasized that the firefighters exonerated in the course of the investigation deserved to be recognized as such.

"Former Mayor Annise Parker rightly said in 2010 that Houston firefighters were 'unjustly under a cloud.' Eight years later, the cloud remains," he said.

"The time has come for authorities to release all of the evidence in this case. Without a proper conclusion, the unjust 'cloud' will undermine a basic tenet of our justice system – innocent until proven guilty."